(532) - At Left Ventricular Assist Device (LVAD) Implantation, Morphologic Differences Are Observed Between Patients With Improved Cardiac Function Allowing LVAD Removal and Patients With Prolonged LVAD Support as a Bridge to Transplantation

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To evaluate differences in morphologic parameters of ventricular remodeling in tissue samples and echocardiograms obtained at left ventricular (LV) assist device (LVAD) implantation in patients who later had sufficient clinical improvement to undergo device explantation versus those who required prolonged continuous-flow (CF) LVAD support and subsequent orthotopic heart transplantation (OHT). We evaluated 25 CF-LVAD patients, 10 of whom had improved cardiac function allowing device removal and 15 of whom underwent long-term device support (>24 months) and subsequent OHT. In all cases, myocardial tissue samples were collected from the LV core obtained at device implantation. Computerized morphometry was used to evaluate fibrosis and hypertrophy, including the cytoplasmic and nuclear diameter. Echocardiographic and hemodynamic parameters at the time of LVAD implantation were correlated with the histopathologic findings. Ten patients (7 men, 3 women; age 30±10 years) had their LVAD (HeartMateII) explanted due to cardiac functional improvement. Fifteen patients (11 men, 4 women; age 46±15 years) underwent OHT after 33±8 months (range: 26-50 months) of CF-LVAD support (HeartMate II, 13 cases; HeartWare, 2 cases). Four patients had ischemic cardiomyopathy, and 11 had nonischemic disease. At LVAD implantation, the LV core from the explant group showed a smaller myocyte diameter (24.55±4.63 vs. 37.09±10.22µ; P=0.0003), a smaller nuclear diameter (12.21±1.72 vs. 15.65±3.88µ; P=0.003), and less fibrosis (10.24±4.03% vs. 17.5±10.36%; P=0.014) than were observed in the transplant group. The left ventricular end-diastolic diameter (LVEDD) was smaller in the explant group than in the transplant group (6.37±0.63 vs. 7.18±1.11 cm; P=0.017). Patients with clinical improvement allowing LVAD explantation had less hypertrophy, less fibrosis, and a smaller LVEDD at the time of LVAD implantation than did patients who required prolonged LVAD support and subsequent OHT. These findings suggest that less extensive morphologic ventricular remodeling changes at LVAD implantation may help determine which subset of patients may have a potential for myocardial reconditioning.